Embodiments of the subject matter disclosed herein correspond to stabilizing arrangements for a rotating vertical shaft, machines with a stabilizing arrangement and stabilizing methods.
In particular, the machines concerned are those commonly used in the field of “Oil & Gas”, mainly subsea single phase or multi phase pumps or compressors; sea water injection is also a possible application of the present invention.
Rotating vertical shafts of machines, especially when shafts are long, are typically subject to radial movements (for example random vibrations) due to lateral asymmetrical actions.
In the field of “Oil & Gas”, vertical shafts are used in turbomachines, such as subsea pumps and compressors, and are typically maintained in position by plain cylindrical or tilting-pad journal bearings. These machines tend to suffer from instability phenomena due to inherent lightly-loaded condition and the vertical orientation of their shafts inside the bearings. Such instability phenomena cause radial vibrations and may lead to damages to the rotor and even its failure.
From the article “Practical use of rotordynamic analysis to correct a vertical long shaft pump's whirl problem” by Mark A. Corbo and Robert A. Leishear in “Proceedings of the 19th International pump users symposium” pages 107-120, “tilting-pad bearings” with a geometric preload are used on a rotating long vertical shaft of a pump to solve the problem of high level of vibrations and “rotordynamic instability”. According to the known operation of “tilting-pad bearings”, one or more of the pads slightly rotate about a vertical axis and thus the rotating shaft remains substantially vertical.
Tilting-pad bearings do not really solve the problem of the instability phenomena due to lightly-loaded and vertical shafts.
Use of bearings eccentrically mounted about the vertical shaft is also known in order to generate a radial load to solve such instability problem.